55000 lines? I guess that explains it...I should have waited longer.
New problem :
When importing animations with their sprites, if the animation contains a sprite more than once, it'll get added to the SFF multiple times instead of once.
For example, importing this range on animations :
;
[Begin Action 2028]
2015,0, 0,0, 1, , A
;
[Begin Action 2029]
2016,0, 0,0, 1, , A
2016,0, 0,0, 1, , AS225D256
2016,0, 0,0, 1, , AS200D256
2016,0, 0,0, 1, , AS175D256
2016,0, 0,0, 1, , AS150D256
2016,0, 0,0, 1, , AS125D256
2016,0, 0,0, 1, , AS100D256
2016,0, 0,0, 1, , AS75D256
2016,0, 0,0, 1, , AS50D256
2016,0, 0,0, 1, , AS25D256
;
[Begin Action 2030]
2016,1, 0,0, 1, , A
2016,1, 0,0, 1, , AS225D256
2016,1, 0,0, 1, , AS200D256
2016,1, 0,0, 1, , AS175D256
2016,1, 0,0, 1, , AS150D256
2016,1, 0,0, 1, , AS125D256
2016,1, 0,0, 1, , AS100D256
2016,1, 0,0, 1, , AS75D256
2016,1, 0,0, 1, , AS50D256
2016,1, 0,0, 1, , AS25D256
;
[Begin Action 2031]
2017,0, 0,0, 1,
resulted in 10 copies of sprite 2016,0 and 2016,1 to be added to the SFF instead of one of each.